Messages in this thread Patch in this message | | | From | Frederic Weisbecker <> | Subject | [PATCH 2/2] perf: Mmap 512 kiB by default | Date | Thu, 31 Mar 2011 03:35:24 +0200 |
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The default setting of perf record is to mmap 128 pages if the user did not override with -m. However the page size may vary accross different architecture settings, giving different default size between each.
Moreover the kernel side still has a default max number of mlocked pages of 512 kiB + 1 page for unprivileged users. 128 + 1 pages with page size > 4096 overlaps this threshold.
Thus, better adapt to this limitation and set the default number of pages to fit those 512 kiB + 1 page.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Paul Mackerras <paulus@samba.org> Cc: Stephane Eranian <eranian@google.com> --- tools/perf/builtin-record.c | 6 +++++- 1 files changed, 5 insertions(+), 1 deletions(-)
diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c index 6febcc1..a7e14bd 100644 --- a/tools/perf/builtin-record.c +++ b/tools/perf/builtin-record.c @@ -41,7 +41,7 @@ static u64 user_interval = ULLONG_MAX; static u64 default_interval = 0; static unsigned int page_size; -static unsigned int mmap_pages = 128; +static unsigned int mmap_pages = UINT_MAX; static unsigned int user_freq = UINT_MAX; static int freq = 1000; static int output; @@ -506,6 +506,10 @@ static int __cmd_record(int argc, const char **argv) if (have_tracepoints(&evsel_list->entries)) perf_header__set_feat(&session->header, HEADER_TRACE_INFO); + /* 512 kiB: default amount of unprivileged mlocked memory */ + if (mmap_pages == UINT_MAX) + mmap_pages = (512 * 1024) / page_size; + if (forks) { child_pid = fork(); if (child_pid < 0) { -- 1.7.3.2
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